This invention relates to an air conditioner which has a heating burner for indirectly heating a refrigerant of the outdoor heat exchanger in an external unit of the air conditioner, wherein the outdoor heat exchanger is used in the heating mode of operation as well as in the cooling mode of operation.
A conventional air conditioning system is illustrated in FIG. 1, which comprises an external unit 8 and an internal unit 9. The external unit 8 has a compressor 81, an outdoor heat exchanger 86 and an expansion tube 83 which are connected in a serial manner. Between the compressor 81 and the outdoor heat exchanger 86 a four way valve 84 is placed. Between the expansion tube 83 and the compressor 82 is installed an auxiliary heat exchanger 82 which is heated by a burner 89, thereby serving a refrigerant circulation in those members when in the heating mode of operation. Further, the internal unit has an indoor heat exchanger 91 which is connected with both the expansion tube 83 and the 4-way valve 84. In the cooling mode (chain arrow C), the gaseous refrigerant compressed by the compressor 81 flows into the outdoor heat exchanger 86 to perform a heat exchange. Next, the gaseous refrigerant is changed into a liquefied state and flows into the expansion tube 83 through the first check valve 87. The liquefied refrigerant via the expansion tube is converted into a low temperature and a low pressure one and flows into the indoor heat exchanger 91. The indoor heat exchanger absorbs heat from the indoors, and the liquefied refrigerant is changed into a gaseous state and passes the second check valve 88 and reaches the compressor 81. During its circulation the cooling mode is achieved. During this operation the burner of the auxiliary heat exchanger 82 is not operated and the two-way valve 85, which is mounted at the front of the auxiliary heat exchanger, is closed.
In the heating mode (solid arrow H), the high temperature and high pressure gaseous refrigerant, which is compressed by the compressor 81, flows into the indoor heat exchanger 91 via the 4-way valve 84. During the heat exchange of the indoor heat exchanger the gaseous refrigerant is changed into a liquefied state. As the two way valve 85 is opened and the operation of the burner 89 starts at this time, the liquefied refrigerant heat-exchanged through the indoor heat exchanger 91 flows into the auxiliary heat exchanger 82 via the two way valve 85. The refrigerant of the auxiliary heat exchanger 82 is heated by the burner 89 to change into the gaseous state and the gaseous refrigerant flows back into the compressor 84. During this cycle, the heating mode is achieved. The typical refrigerant heating type air conditioners are disclosed in U.S. Pat. Nos. 4,506,521 and 5,174,365.
However, because an auxiliary heat exchanger, which is comprised of the additional part of the outdoor heat exchanger, is employed in the heating cycle of the above described air conditioner, there is a problem in that a complex structure is required. Further, during the initial operation of the heating mode, there is a problem in that the refrigerant is collected from the outdoor heat exchanger to prevent the heating efficiency from decreasing.